Fluid actuated switching device



March 18, 19,69 M. F. PRAVDA Q I FLUID ACTUATED SWITCHING DEVICE FiledJuly 18, 1966 7 Sheet of 2 FIT5=1 4e FIE-.- 2 I 4 {7 I I r-" 30 a2INVENTOR MILTON FRANK PRAVDA h 1 Attorney Sheet 2 of March 18, 1969 M.F. PRAVDA FLUID ACTUATED SWITCHING DEVICE Filed July 18. 1966 l m. m5 aUnited States Patent 3,433,910 FLUID ACTUATED SWITCHING DEVICE MiltonFrank Pravda, Solon, Ohio, assignor to Cleveland Controls, Inc.,Cleveland, Ohio, a corporation of Ohio Filed July 18, 1966, Ser. No.566,063 US. Cl. 200-83 11 Claims Int. Cl. H01h 35/24, 35/40 ABSTRACT OFTHE DISCLOSURE A fluid actuator and switching device combination. Theactuator is formed of a pair of flat plates with a gasket and diaphragminterposed therebetween. The switch is independently formed and mountedon the actuator. The switch and diaphragm have coacting means to operatethe switch as the pressure varies. In one embodiment the actuator itselfacts as a conduit as a part of the fluid circuit. Also, optionaladjustment means for changing the operating pressure are provided.

This invention relates generally to switching devices and moreparticularly to fluid actuated electrical switching devices which willprovide electrical signals when the fluid pressure exceeds preselectedvalues.

The switching device of this invention has particular significance inuse with control devices for therapeutic air mattresses wherein parallelair chambers within the mattress are alternately inflated and deflatedto prevent bed sores from forming on a patient. However, the use of thisdevice is not so limited, and finds application wherever electricalswitching is necessary responsive to changes in fluid pressure.

Briefly, the switching device of this invention includes a pair ofopposed rigid plates which are separated by a sealing gasket. Adiaphragm is interposed between the sealing gasket and one of theplates, and that one plate has an opening therein to allow for movementof the diaphragm responsive to change in flui'd pressure acting on it.An electrical switch is mounted in a position to be actuated by movementof the diaphragm responsive to fluid pressure changes acting on thediaphragm. The switch may be wired to give visual or audible signals ofdifferent types when the fluid pressure acting on the diaphragm exceedsa given value or is less than a given value or the switches may be usedfor control functions.

Still other advantages of the invention and the invention itself willbecome more apparent from the following description of severalembodiments thereof, which description is illustrated by theaccompanying drawings and forms a part of the specification.

In the drawings:

FIG. 1 is a plan view of an embodiment of a fluid actuated switchingdevice according to this invention;

? FIG. 2 is a side elevational view of the switch of FIG. 1;

FIG. 3 is a bottom plan view of the switch of FIG. 1;

FIG. 4 is a sectional view taken substantially along the planedesignated by line IV-IV of FIG. 1, showing some movement of thediaphragm;

FIG. 5 is a sectional view similar to that of FIG. 4 with the diaphragmand switch in a different position;

FIG. 6 is a sectional view taken substantially along the planedesignated by line VIVI of FIG. 4;

FIG. 7 is a sectional view of another embodiment of a switching deviceaccording to this invention;

FIG. 8 is a sectional view similar to FIG. 7, showing the switch anddiaphragm in a different position;

FIG. 9 is a sectional view similar to FIG. 8' with the sensitivitybracket adjusted to a ditferent position;

FIG. 10 is a sectional view taken substantially along the planedesignated by line XX of FIG. 7; and

FIG. 11 is a bottom plan view of a group of two switches utilizingcommon plates, gaskets, an'd diaphragms.

Referring now to the drawings, and for the present FIGS. 1 through 6,one embodiment of a fluid actuated switching device according to thisinvention is shown. The switching device includes a pair of superposedrigid metal plates 10 and 12. The plate 12 is provided with a centralrectangular opening 14, and a rectangular sealing gasket 16 having arectangular opening 17 corresponding to opening 14 is provided betweenthe plates 10 and 12. A diaphragm 18 is interposed between the sealinggasket 16 and the plate 12, and the plates 10 and 12, the gasket 16, andthe diaphragm 18 are all secured together in superposed relationship bya pair of screws 20 and nuts 22. A stop bracket 24 is secured to theunderside of the plate 12, and has an arm 26 extending parallel with thediaphragm 18. The sealing gasket 16 is formed of a thick, resilientrubber-like material preferably having a thickness of between an eighthof an inch and a quarter of an inch. Because of the thickness of thegasket 16, a fluid receiving space 28 is defined between the diaphragm18 and the plate 10. A pair of fittings 30 and 32 are secured to theplate 10 and communicate with the space 28. The fittings 30 and 32 areadapted to receive suitable fluid conducting tubes as shown in dottedlines. A rigid, non-conducting plastic strip 34 is secured to the lowerside of the diaphragm 18 by an epoxy resin.

An electrical switch generally designated as 36, is mounted on thescrews 20 beneath the plate 12, and is secured on the screws 20 by nuts38. Spacer sleeves are provided between the switch 36 and the nuts 22 toproperly position the switch 36 in relation to the diaphragm 18. Theswitch per se, forms a part of this invention, and any of severalswitches may be utilized. It will also be appreciated that thecombination is not limited to electrical switches, and the term switchas used herein is intended to include indicating, controlling, orpositioning devices, such as gages, valves, or the like. It has beenfound that for electrical switching switch SK-3, manufactured by MicroCorporation of Freeport, 111., is quite satisfactory. This switch has arigid support base 42 on which is mounted an L-shaped bracket 44. Thebracket 44 pivotally mounts an actuating arm 46 which is normally biasedby spring contact arm 48 toward the diaphragm 18 against the strip 34into the position shown in FIG. 2. In the case of electrical switches,it is important that the actuating arm 46 be insulated from the plates10 and 12 to prevent short circuitry. This isolation is assured by theadhesive mounting of the non-conducting plastic strip 34. The contactarm 48 has an electrical contact point 50 which is movable with thecontact arm 48 into and out of engagement with an electrical contact 52secured to the base plate 42. A second electrical contact 54 is providedon the support base 42, and the contact arm 48 is movable vertically tomove the contact point 50 between the contacts 52 and 54. A bowedportion 56 of the contact arm 48 provides the spring bias which normallyurges the contact arm into its position as shown in FIG. 2. Theconstruction and action of the switch 36 is such that the actuating arm46 will move an appreciable distance downwardly with the contact arm 48remaining in its position as shown in FIG. 2, with the contact point 50resting on and urged into engagement with contact 54 as shown in FIG. 4.When the actuating arm 46 is moved past this point, the contact arm 48will pivot about bracket 44 and snap the contact point 50 againstcontact 52. This then constitutes a switched position of the electricalswitch 36. Further movement of the arm 46 will increase the pressureholding the contact point 50 against contact 52 as shown in FIG. 5.

Conversely, from position at which point switching has just taken place,as shown in FIG. 4, appreciable upward or return movement of theactuating arm 46 is required before the contact arm 48, under the urgingof the bowed portion 56, will snap the contact point 50 back againstcontact 54 to its original position. Since the movement of the actuatingarm 46 is responsive to movement of the diaphragm which in turn isresponsive to the pressure in space 28, switching from the position ofthe contacts shown in FIG. 2 to the position shown in FIG. 5 will occurat a higher pressure value than switching back from the position of thecontacts in FIG. 5 to the position shown in FIG. 2.

As is shown in FIG. 3, contact 52 is connected through a battery 58 (orother source of power) and lamp 60 to the bracket 44. When contact point50 engages contact 52 as shown in FIG. 5, a circuit is completed and thelamp 60 will glow.

Turning now to the operation of the device, the embodi ment shown inFIGS. 1 through 6 acts not only as a sensor of fluid pressure but theswitching device itself acts as a conduit through which the pressurefluid is delivered. The tubing delivering the air or other pressurefluid is connected as shown in the drawings so that the air from thesource of pressure fluid enters one fitting, passes through the space 28and out the other fitting to the object being supplied with air such asa therapeutic air mattress. The fluid delivered to the space 28 exerts apressure equal to the pressure of the fluid on the diaphragm 18 causingthe diaphragm to tend to move away from the plate 12, urging the plasticstrip 34 against the actuating arm 46 of the electric switch 36. As thepressure increases the diaphragm forcing against the actuating arm 46moves the arm 46 a distance proportional to the increase in pressure.When the pressure is sufficient to move the arm 46 past the positionshown in FIG. 4, the contact arm 48 will move the contact point 50 fromcontact 54 and into engagement with contact 52. This point represents agiven pressure level in the space 28, and a circuit is established tolight the lamp 60. Of course, a buzzer or indicia may be wired into thecircuit in a conventional manner in place of or in addition to a lamp togive an indication that the switch has switched. Also, the switch mayserve to operate control devices responsive to sensed pressure.Increased pressure beyond this point where switching occurs will causethe diaphragm to continue to move away from the plate 10 until theplastic strip 34 comes in contact with the stop bracket 24 at whichpoint motion of the diaphragm is halted, as shown in FIG. 5. It isdesirable to halt this motion of the actuating arm 46 by this bracket toprevent the arm 46 from being forced down against the top of contact 52,since repeated extended motion of the arm 46 in this fashion greatlyreduces the life of the electrical switch 36.

From this switched position, as shown in FIG. 5, a decrease in pressurewill cause the actuating arm 46 to bias the diaphragm 18 back toward theplate 10. As the pressure decreases, the bias of the bowed portion 56will cause the actuating arm 46 to move upwardly a distance proportionalto the drop in pressure. This movement will continue past the positionat which switching occurred into the switched position represented inFIG. 4 until another position is reached which represents a pressurevalue lower than the value at which the switching occurred. At thisother position the contact arm under the bias of bowed portion 56 willbe moved to snap contact 50 back against contact 54. Thus the device ofthis invention will switch the contacts to position shown in FIG. 5 fromthat of FIG. 2 :at a higher pressure level than it will switch thecontacts back to the position shown in FIG. 2 from that shown in FIG. 5.This feature is particularly advantageous when the switch is used inconjunction with the control of therapeutic air mattresses to providevisual indications of air leaks from either of the two systems. Thereare other instances also where this type of switching action atdifferent levels, depending on whether pressure is increasing ordecreasing, is desired.

Turning now to the embodiment shown in FIGS. 7 through 10, thecomponents are the same except that the arm 26 of the stop bracket 24has a turned up end portion 26a, the point of which comes close to butdoes not touch the plastic strip 34. The stop bracket 24 is alsoprovided with an elongated slot 24a which allows the bracket 24 to beadjusted to change the position of the turned up portion 26a withrespect to the plastic strip 34. Also this embodiment illustrates theuse of the device merely as a pressure sensing device, and not as apassage for the pressure fluid. To this end, but a single fitting 30 isprovided. In this embodiment, the fitting 30 is connected directly tothe container of the pressure fluid and the device acts solely as apressure gauge and not as a conduit through which fluid flows.

Turning now to the operation of the device shown in FIGS. 7 through 10.When the pressure in the space 28 starts to increase, it will move thediaphragm 18 away from the plate 10 just as described with respect tothe previous embodiment. However, the plastic strip 34 will encounterthe turned up lip 26a of the stop bracket 24 before the actuating arm 46has caused the contact point 50 to switch as shown in FIG. 7. Anyfurther movement of the diaphragm will cause a pivotal movement of theplastic strip 34 about the turned up lip 26a and the force required forthis motion is greater than to move the plastic strip 34 away from theplate without any obstruction. Pivotal motion will cause the switch toswitch to the position shown in FIG. 8. The amount of force required tocause the pivotal motion of the plastic strip 34 depends upon the pointof engagement thereof, by the upturned lip 26a of the stop bracket 24.The closer the lip 26a is to the center of the plastic strip 34, thegreater will be the force required for such pivotal movement. Theelongated slot 24a allows for the positioning of the stop bracket 24 toselect this point of engagement of the lip 26a and hence select theamount of pressure required to move the plastic strip pivotally aboutthe upturned lip 26a. This then allows for the adjustment of thepressure at which switching will occur from the position shown in FIGS.7 and 8 to that shown in FIG. 9. In this way the sensitivity of theswitching device for switching from one position to another at the highpressure end can be adjusted. Of course, the pressure needed to switchback on the return of the actuating arm 46 will be the same irrespectiveof the position of the stop bracket 24.

Another modification is shown in FIG. 11. In this embodiment a pair ofplates, a single gasket, and a single diaphragm mount and actuate a pairof switches. This has the advantage of providing a compact, integralunit of a multiplicity of switches, and is particularly useful inconjunction with a therapeutic mattress where two different fluidpressure containing systems are alternately inflated and deflated.

In the embodiment of FIG. 11 a pair of plates and 112 are provided. Theplate 112 is provided with a pair of rectangular openings 114side-by-side. A Sealing gasket 116 is provided which has a pair ofrectangular openings 117 coresponding to openings 114. A diaphagm 118 isinterposed between the sealing gasket 116 and the plate 112. The platesare held together by four screws 120. A stop bracket 124 is secured tothe underside of the Plate 112 and has an arm 126 extending parallelwith the diaphragm 118. Fluid receiving spaces 128 are defined in eachof the openings 117, and a pair of fittings 130 and 132 are secured tothe plate 110 adjacent each space 128 and communicating with them. Thediaphragm is provided with a pair of plastic strips 134. The fittings130 and 132 are laterally ofi-set with respect to the strips 134. Thismodification, which can also be incorporated in the previously describedembodiments, prevents the passage from being blocked by the rigidly helddiaphragm beneath the plastic strip 134 when the switches hold thediaphragm against the plate 110. A pair of electrical switches 136 ofthe type previously described are mounted in the same manner aspreviously described with spacers (not shown) and nuts 138 adjacent eachplastic strip 134. Although the switches 136 are commonly mounted, theyare independently actuated by fluid to each of the spaces 128, which areisolated from each other, The switching device is compact and can beconstructed inexpensively. It is obvious too, that three or moreswitches could also be commonly mounted when necessary.

While several embodiments of this invention have been shown anddescribed, various adaptations and modifications can be made withoutdeparting from the scope of the appended claims.

I claim:

1. A switching device comprising in combination, a switch having firstand second positions and a fluid actuator therefor, said fluid actuatorhaving first and second opposed flat plates, said first plate having anopening therein, a sealing gasket interposed between said plates andhaving a central opening, a diaphragm secured between said gasket andsaid first plate and with said gasket and said second plate defining afluid receiving space, fluid conducting means communicating with saidspace, said diaphragm being movable toward and away from said secondplate responsive to changes in fluid pressure in said space, said switchhaving a mounting plate secured to said first plate, said diaphragm andsaid switch having co-acting means to move said switch into its secondposition when the fluid pressure in said space exceeds a preselectedvalue and to move said diaphragm toward said second plate and saidswitch into its first position when the pressure in said space is lessthan a preselected value.

2. The combination of claim 1, wherein said coacting means includes arigid plastic strip secured on said diaphragm.

3. The combination of claim 1, further characterized by adjusting meansto adjust the force required to move said switch to said secondposition, and wherein said adjusting means includes fulcrum meansdisposed to operatively engage said strip and means to selectivelyposition the place of engagement, whereby the pressure value required tomove the switch to its second position can be varied.

4. A unitary switching device comprising in combination, first andsecond switches each having first and second positions and fluidactuators therefor, said fluid actuators having first and second opposedplates, said first plate having a pair of openings therein, .a sealinggasket interposed between said plates and having a pair of centralopenings corresponding to said openings in said first plate, a diaphragmsecured between said first plate and said gasket and with said secondplate and said gasket defining first and second fluid receiving spaces,the diaphragm portion adjacent each fluid receiving space being movabletoward :and away from said second plate independently responsive tochange in pressure in its defined fluid receiving space, said switcheshaving mounting plate means secured to said first plate, each diaphragmportion and one of said switches having co-acting means to move therespective switch into its second position when the fluid pressure inthe respective space exceeds a preselected value and to move thediaphragm toward the second plate and the switch into its first positionwhen the pressure in the respective space is less than a preselectedvalue.

5. The combination of claim 1, further characterized by means detachablysecuring said mounting plate of said switch to said first plate.

6. The combination of claim 5 further characterized by said first andsecond plates being interconnected by screw means and said mountingplate for said switch being carried by said screw means.

7. The combination of claim 5, further characterized by spacer meansinterposed between said mounting plate of said switch and said firstplate.

8. The combination of claim 1, further characterized by said fluidconducting means including fluid inlet and fluid outlet means, wherebysaid actuator serves as a fluid conduit.

9. The combination of claim 8, wherein said fluid inlet and outlet meansinclude spaced apertures in said second plate.

10. The combination of claim 4, wherein each of said switches has amounting plate and each mounting plate is mounted for independentremoval from said first plate.

11. The combination of claim 10, wherein said screw means interconnectssaid first and second plates, and the mounting plate and said switchesare carried by said screw means.

References Cited UNITED STATES PATENTS 3,178,531 4/1965 Dawson et a1.200---83.9 3,267,233 8/1966 Brasile et a1. 20083.8

FOREIGN PATENTS 1,011,437 12/1965 Great Britain.

ROBERT K. SCHAEFER, Primary Examiner.

H. BURKS, Assistant Examiner.

